Heterochromatin is a major component of higher eukaryotic genomes and plays an important role in chromosomes and cell biology. Errors in chromosome inheritance and rearrangements involving heterochromatin are associated with a variety of human disorders. The knowledge base of heterochromatin structure and function is limited due to the lack of detailed molecular information about this important genomic component. A 1 Mb heterochromatic region of the 1.3 Mb Drosophila minichromosome Dp1187 represents a model for heterochromatin studies. The aims of this proposal are to further characterize this region as an extension of previous studies. They include the following: 1) complete the sequence analysis of the 420 kb centromere, a key component of chromosome inheritance in all eukaryotes; 2) generate tools and information to initiate the mapping and sequence analysis of many other regions of Drosophila heterochromatin, and 3) collaborate with FlyBase, a Drosophila internet database resource, to collect and integrate information about Drosophila heterochromatin.